Spirometers are medical instruments which measure inhalation or exhalation flow rates and volumes of the human lung. These typically utilize a rotating device to detect air flows.
However, many spirometers are not realistically designed for the range of applications to which they may be subjected, for example, users with lung infections, or frail users, or users who do not have the capacity to follow verbal directions from a respiratory technician, or use under the direction of a respiratory technician who may not provide proper instruction.
In fact, the results of readings from human-generated air flow can vary as much as twenty percent due to poor inhalation/exhalation maneuvers by the patient, i.e., poor effort and timing of the breath cycle.
Also, the mouthpieces of many spirometers are typically oriented in a manner that makes it more difficult or uncomfortable to properly use and therefor to obtain accurate breathing readings. Similarly, mouthpieces are typically cumbersome to use and do not conform well to the user's mouth.
Known spirometers also do not typically contain adequate safeguards against users who have lung diseases which might contaminate the spirometer, to protect the respiratory technician and subsequent users.
Also, spirometers typically introduce their own resistance and/or back pressure into the air flow path, which can result in inaccurate readings, particularly for a feeble user. Air flow turbulence is also a problem, and can result in reading variations on the order of 15% to 20% for identical air flow rates for a given spirometer calibration.
There are in fact several distinct readings all of which are pertinent to measuring the breathing capacity of the user, which known spirometers typically do not provide as a whole. These include, but are not limited to: total lung volume, peak flow rate, flow rate at the end of a predetermined elapsed time (e.g., one second), and total flow volume after a predetermined period (e.g., fifteen seconds) of multiple breathing maneuvers.
Many spirometers are also of use in a limited range of settings. For example, basic hand-held spirometers often cannot be used in a hospital bedside environment for continuous breathing monitoring. For spirometers used in a hospital setting, the readings taken can sometimes be mismatched with the wrong patient due to personnel errors.
Many spirometers must be held with two hands, and are wired to nearby computation, display and printout devices. The close proximity of these devices as well as the proliferation of wires, may worry or confuse a patient, thus compromising the patient's inhalation or exhalation maneuvers.
In many instances, air expelled through the spirometer blows away from the spirometer user and towards others, which can infect a technician or other person nearby.
Also, spirometers do not typically have a filter with an indicator that would allow someone to determine if that filter has already been used, and thereby prevent reuse of an infected filter.
Multilayer or electronic biostatic filters that might be used for a spirometer are costly to manufacture, and alternatives to this can reduce cost.
Also, the human breath has a comparatively high moisture content with respect to atmospheric air, which acts as a lubricant for the rotating element and distorts the readings of existing spirometers.
Existing spirometers often do not shut down after use, which result in unnecessary power loss. Nor do they provide simple means to calibrate the rotating element.
Finally, because of the filters they employ, existing spirometers are frequently very large, heavy and cumbersome.